Presenter:

Authors:

Catalin Spataru(Materials Physics, Sandia National Labs)

Shiyuan Gao(Physics, Washington University)

Li Yang(Physics, Washington University)

Bilayer van der Waals heterostructures such as MoS2/WS2 and MoSe2/WSe2 have attracted much attention recently, particularly because of their type II band alignments and the formation of interlayer exciton as the lowest-energy excitonic state. Here, we calculate the electronic and optical properties of such heterostructures with the first-principles GW+Bethe-Salpeter Equation method and reveal the important role of interlayer coupling in deciding the excited-state properties, including the band alignment and excitonic properties. Our calculation shows that due to the interlayer coupling, the low energy excitons can be widely tunable by a vertical gate field. In particular, the dipole oscillator strength and radiative lifetime of the lowest energy exciton in these bilayer heterostructures is varied by over an order of magnitude within a practical external gate field. Then we build a minimal model that captures the essential physics behind this tunability and allows the extension of the ab initio results into a larger range of electric fields.

*This work is supported by the LDRD program at Sandia National Labs, a multimission laboratory managed and operated by NTESS for DOE’s NNSA under contract DE-NA-0003525. S.G. and L.Y. are also supported by the NSF CAREER Grant DMR-1455346.